Their system status page provides details of any issues affecting Turnitin and the time it took place. They are published using Twitter. You can choose to follow them @TurnitinStatus or sign up to receive email alerts.

Time conversion: Times shown in the Twitter status updates relate to USA time – PDT (Pacific Daylight Time) or PST (Pacific Standard Time). Convert the time shown using this link: Time Zone Converter (Use ‘USA – California – San Francisco’ as the place to convert from.)